Hide Secrets Mode

Experimental feature that prevents LLM agents from seeing raw secrets in your project files and environment variables.

What It Does

When enabled, Construct creates an isolated workspace where:

Project files containing secrets are redacted (values replaced with CONSTRUCT_REDACTED_<HASH>)
Environment variables with secret names are masked for the agent
The agent cannot access raw secrets, only the masked versions
Your original project files remain unchanged

Security Guarantee

Core guarantee: When hide-secrets mode is enabled, the agent process must not have direct access to raw project secrets by default.

This protects against:

Agents reading .env files and printing secrets
Agents copying credentials to output
Accidental leakage in logs and terminal output
Tools that display environment variables

Quick Start

1. Enable the Feature Gate (Required)

Set the environment variable:

export CONSTRUCT_EXPERIMENT_HIDE_SECRETS=1

2. Configure in `config.toml`

[security]
hide_secrets = true
hide_secrets_mask_style = "hash"

3. Run Construct Normally

construct claude "Help me debug my API code"

The agent will now see redacted secrets instead of real values.

Configuration Options

Basic Settings

[security]
# Master switch (requires CONSTRUCT_EXPERIMENT_HIDE_SECRETS=1)
hide_secrets = false

# Mask style: "hash" (default) or "fixed"
hide_secrets_mask_style = "hash"

# Emit session report after each run
hide_secrets_report = true

# Hide .git directory (recommended)
hide_git_dir = true

Mask Styles

Hash (default): Unique placeholder per secret

Before: DATABASE_URL=postgresql://user:pass123@localhost/db
After:  DATABASE_URL=CONSTRUCT_REDACTED_A1B2C3D4

Better for debugging - you can identify which secret was redacted.

Fixed: Static placeholder

Before: DATABASE_URL=postgresql://user:pass123@localhost/db
After:  DATABASE_URL=CONSTRUCT_REDACTED

Maximum secrecy - all secrets look identical.

Advanced Configuration

Force-Scan Specific Files

# Always scan these files for secrets, even if they don't match heuristics
hide_secrets_deny_paths = [
    "**/secrets.yml",
    "**/.env.local",
    "config/prod/*.yaml"
]

Exclude Files from Redaction

⚠️ DANGER: Files in this list will NOT be redacted - secrets will be visible to agents.

# Use ONLY for files that tools must read directly
hide_secrets_allow_paths = [
    "~/.aws/credentials",  # AWS CLI needs this
    "config/tool-specific-secrets.yaml"
]

Warning: This breaks the security model for allowlisted files. Use sparingly.

Environment Variable Passthrough

# These env vars will be visible to agents in raw form
hide_secrets_passthrough_vars = [
    "PUBLIC_API_URL",
    "APP_ENV",
    "NON_SECRET_CONFIG"
]

What Gets Scanned

Automatically Scanned Files

Construct scans files matching these patterns:

.env, .env.*
*.pem, *.key, *.p12, *.pfx, id_rsa, id_ed25519
.npmrc, .pypirc, .netrc, .dockercfg
*.tfvars, *.tfvars.json
application*.yml, application*.yaml, application*.properties
config*.json, config*.yaml, config*.yml, config*.toml, *.ini

Secret Indicators

Files are scanned for keys containing:

api_key, apikey, api-key
secret, password, passwd, pwd
token, auth, authorization
dsn, connection_string, connection-string
private_key, private-key, privatekey
credential, cert, certificate

Provider-Specific Patterns

Construct also detects:

GitHub tokens: ghp_
OpenAI keys: sk-
Anthropic keys: sk-ant-
AWS keys: AKIA
Stripe keys: sk_live_/pk_live_
Slack tokens: xoxb-
Private key blocks: -----BEGIN [A-Z]+ PRIVATE KEY-----

Use Cases

✅ Good Use Cases

Debugging API code without exposing API keys

construct claude "Debug why my API calls are failing"

Code review of authentication logic

construct claude "Review my authentication flow for security issues"

Working with sensitive projects

construct claude "Help me refactor this database migration code"

❌ When NOT to Use

When tools need direct secret access

AWS CLI (~/.aws/credentials)
kubectl (~/.kube/config)
Tools that read credentials files directly

Use hide_secrets_allow_paths for these files, or disable hide-secrets mode entirely.

When agents need to make authenticated API calls

This is handled via the provider proxy (future enhancement)
For now, use standard mode for workflows requiring API calls

Session Behavior

Read-Only Sessions

In hide-secrets mode:

Agent runs in an isolated workspace (OverlayFS on Linux, APFS clones on macOS)
Agent writes do not persist to your real project
Changes remain in session workspace only
On session end, you'll see a warning if there are changes

Example output:

⚠️  Hide-secrets session ended with changes
   Files changed: 3
   Session directory: ~/.config/construct-cli/security/sessions/abc123
   Changes were NOT written to the real project.
   Review changes in the session directory.

Session Cleanup

Sessions are automatically cleaned up:

Unchanged sessions: Deleted immediately
Changed sessions: Retained for manual review
Crashed sessions: Detected via PID checks and cleaned after grace period

Example Workflows

Debugging with Secrets

# 1. Enable hide-secrets mode
export CONSTRUCT_EXPERIMENT_HIDE_SECRETS=1

# 2. Run agent
construct claude "Debug my database connection code"

# Agent sees:
# DATABASE_URL=CONSTRUCT_REDACTED_A1B2C3D4
# API_KEY=CONSTRUCT_REDACTED_D4E5F6A7

# Your actual .env file:
# DATABASE_URL=postgresql://user:realpass@localhost/db
# API_KEY=sk-1234567890abcdef

Working with AWS CLI

[security]
hide_secrets = true
# Allow AWS CLI to access credentials
hide_secrets_allow_paths = ["~/.aws/credentials"]

construct claude "Use AWS CLI to list S3 buckets"
# Agent can run: aws s3 ls
# But other secrets remain redacted

Multi-Environment Projects

[security]
hide_secrets = true
hide_secrets_deny_paths = [
    "config/prod/*.yaml",
    "config/staging/*.yaml"
]

Troubleshooting

Feature Not Working

Check: Is the environment gate set?

echo $CONSTRUCT_EXPERIMENT_HIDE_SECRETS
# Should output: 1

Check: Is hide_secrets = true in config?

construct sys doctor | grep hide_secrets

Tools Failing in Hide-Secrets Mode

Problem: AWS CLI, kubectl, or similar tools failing

aws: Unable to locate credentials

Solution: Add credentials file to allowlist

hide_secrets_allow_paths = ["~/.aws/credentials"]

Too Many False Positives

Problem: Non-secret values being redacted

Solution: Use passthrough for specific env vars

hide_secrets_passthrough_vars = ["PUBLIC_API_URL", "APP_NAME"]

Session Changes Not Persisting

This is intentional behavior in hide-secrets mode.

To persist changes:

Review changes in session directory
Manually copy desired changes to your project
Or disable hide-secrets mode for that workflow

Security Best Practices

✅ DO

Use hide-secrets mode when debugging or reviewing code
Keep .git hidden (hide_git_dir = true)
Use hash mask style for easier debugging
Review allowlist entries carefully
Keep CONSTRUCT_EXPERIMENT_HIDE_SECRETS=1 env-only (don't add to shell profiles)

❌ DON'T

Add all config files to allowlist (defeats the purpose)
Use hide_secrets_allow_paths for files you don't control
Commit actual secrets to git (even with hide-secrets enabled)
Assume hide-secrets mode prevents all secret leaks (defense-in-depth)

Limitations

What's Protected (V1)

✅ Project files with secret values
✅ Environment variables with secret names
✅ Output from Construct-controlled subprocesses
✅ .git directory (when hide_git_dir = true)

What's NOT Protected (V1)

❌ Secrets already in git history
❌ Binary/archive files (not scanned)
❌ Provider API calls (requires proxy feature, V2)
❌ Malicious host-side tools outside Construct
❌ Subprocess output from non-Construct tools

Future Enhancements (V2+)

Provider proxy for authenticated API calls
Daemon isolation for stronger security boundaries
Advanced proxy policy controls
Organization-level policy presets

Technical Details

Workspace Isolation

Linux: Uses OverlayFS

Lower layer (real project, read-only)
  ├── .env          ← Contains real secrets
  └── src/          ← Regular files

Upper layer (session-specific, writable)
  ├── .env          ← Redacted copy (CONSTRUCT_REDACTED_*)
  └── changes/      ← Agent writes

Merged view (agent workspace)
  ├── .env          ← Shows redacted version
  └── src/          ← Passthrough from lower

macOS: Uses APFS clones (copy-on-write) with similar isolation

Audit Logging

Security events are logged to:

~/.config/construct-cli/security/audit/security-audit.log

Events include:

Session start/end
Token mint/revoke
Redaction operations
Policy violations

View audit logs (V2):

construct sys security audit verify

Getting Help

Issues: Report bugs at github.com/EstebanForge/construct-cli/issues
Security concerns: Use private security disclosure
Feature requests: Welcome via GitHub issues

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